Nowadays the use of laundry washing machines, both “simple” laundry washing machines (i.e. laundry washing machines which can only wash and rinse laundry) and laundry washing and drying machines (i.e. laundry washing machines which can also dry laundry), is widespread.
In the present description the term “laundry washing machine” will refer to both simple laundry washing machines and laundry washing and drying machines.
Controlling the amount of washing water supplied to a laundry washing machine is an important issue, especially nowadays that electric energy consumption and, in general, environmental responsibility are very felt.
Controlling the amount of washing water supplied is very important for example to determine the correct quantity of washing liquid for washing the clothes, wherein with washing liquid it is meant the mix of fresh washing water and detergent supplied into the washing tub where the laundry is arranged.
The washing water is preferably supplied into the washing tub through a controllable dosing device, e.g. a valve, preferably an electrovalve. In some known solutions, a metering device, for example a flowmeter, is advantageously connected to the electrovalve outlet. The electrovalve is switched on and off by a control unit, which also receives data from the flowmeter. Data from the flowmeter are detected while the valve is switched on. The amount of water introduced is calculated from data detected by the flowmeter.
The correct amount of detergent to be used in the washing liquid is based on the amount of washing water supplied, typically as a percentage of the latter and/or according to the washing cycle selected by the user.
Therefore, a wrong determination of the amount of washing water supplied into the washing tub also causes a wrong determination of the amount of detergent to be used.
This may cause the worsening of the clean effect in the washing cycle and/or the use of more washing water and/or detergent than necessary, with increased costs and negative environmental impact.
In addition, the possibility to accurately detect the amount of washing water supplied into the machine is a crucial aspect in the automatic determination of the quantity of clothes and of the type of fabric introduced in a laundry washing machine.
As known, the knowledge of the fabric type and the quantity of clothes introduced in a laundry washing machine are of a substantial importance in order to select best washing program.
Said information may be transmitted to the laundry washer control-system directly by the user, through appropriate means (such as keyboards with display, indexed knobs, keys, etc.), or can be automatically obtained by the control system itself, when the latter is technologically appropriate to this purpose (e.g. including an electronic microprocessor control system).
In the latter case, the measure of the quantity of clothes and the type of fabric can be performed either directly or indirectly.
A direct measurement method appears stricter but difficult to implement, as some sophisticated and expensive sensors are required, whereas an indirect measurement method better complies with the low-cost and moderate accuracy requirements as demanded by a commercial laundry washing machine.
Some methods of indirect measurement of the fabric type and/or the quantity of clothes introduced in a laundry washing machine are known, which are based on the software elaboration of data information being generated by proper settings of the process of water inlet inside the laundry washing machine.
Said methods are based on the physical capacity of fabrics to absorb water, according to a procedure based on their quantity and fibre type.
In particular, it is known from experimental results that a fabric type considerably affects the water initial absorption speed inside the washing tub, whereas the total quantity of water absorbed under saturation conditions is a function of both the quantity of clothes and fabric type (i.e. sponge-cloth, cotton. synthetics, silk, wool, etc.).
German patent application DE-A-4.122.307 discloses an indirect measurement method as mentioned above. According to said method, the control system of a laundry washer elaborates the data information supplied by an electromechanical level sensor (pressure switch) during the initial phases of a washing cycle; such data information relate to the water level restoring process in the washing tub of the laundry washer.
The water level restoring process requires a plurality of phases of water inlet into the washing tub. Each water inlet phase is followed by a phase of water absorption by the laundry.
During the water inlet phases, an amount of water is introduced through a valve, preferably an electrovalve, into the washing tub. A metering device, for example a flowmeter, is advantageously connected to the electrovalve outlet. The electrovalve is switched on and off by a control unit, which also receives data from the flowmeter. Data from the flowmeter are detected while the valve is switched on. The amount of water introduced during each water inlet phase and the amount of water totally introduced in the water inlet phases is calculated from data detected from the flowmeter.
However, the technique above described belonging to the known art poses some drawbacks.
A first drawback of this known technique is the fact that the valve (electrovalve) closes with a delay time with respect to the switching off signal sent by the control unit.
Due to this delay time the water continues to flow through the valve, resulting in an extra quantity of water loaded.
The control unit does not take into account this extra quantity of water. An extra quantity of water is then repeatedly introduced into the washing tub in case of a plurality of water inlet phases. The amount of water introduced during each water inlet phase and the amount of water totally introduced in the water inlet phases is therefore not correctly calculated.
The same problems arise when water inlet phases are used in laundry washing machines equipped with a water softening device. In this case the water is supplied to a regeneration-agent reservoir.
In the techniques of known art, therefore, the real amount of water introduced in the washing tub is not accurately detected and/or calculated. This negatively affects different steps of the washing cycle: the step of determining the proper quantity of detergent to be added to the washing water; and/or the step of determining the heating time of the washing liquid, i.e. water and detergent, during the washing phase; and/or the step of determining the quantity of clothes and/or the type of fabric introduced in the laundry washing machine. In case the laundry washing machines are equipped with a water softening device, this can also negatively affect the step of supplying water to the regeneration-agent reservoir.
The object of the present invention is therefore to overcome the drawbacks posed by the known technique.
It is a first object of the invention to implement a method for operating a laundry washing machine that makes it possible to properly control the amount of water supplied to the washing machine.
It is an object of the invention in particular to implement a method that makes it possible to control the exact amount of washing water supplied to the washing machine.
It is another object of the invention to implement a method that makes it possible to proper determining the quantity of clothes and/or the type of fabric introduced in the laundry washing machine.
It is a further object of the invention to implement a method that allows determining the proper quantity of detergent to be added to the washing water.
It is another object of the invention to implement a method that allows determining the proper heating time of the washing liquid, i.e. water and detergent, during the washing phase.
It is a further object of the invention in particular to implement a method that makes it possible to control the correct amount of water supplied to a water softening device, in particular to a regeneration-agent reservoir of the latter, of the laundry washing machine.
Advantages, objects, and features of the invention will be set forth in part in the description and drawings which follow and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.